Coke employed in the iron making process is required in such large quantities that it must be handled in bulk. The bulk handling methods employed are such that the relatively brittle chunks of coke break up to product a substantial quantity of fines or particles which are too small to be fed into the cupola. Coke particles below a minimum size simply tend to be blown up through the cupola stack, and hence it is conventional practice during the feeding of the coke to the cupola to subject the coke to a screening process which separates the fines out of the coke before they are fed into the cupola.
Typically, the fines thus separated represent about 10 percent of the total amount of the coke fed to the cupola. Normally, the separated fines are subjected to a second screening operation which separates the powdery material from the larger fines. The larger fines recovered from this screening process can usually be sold at a price of about 60 percent of the price of raw coke, while there is very little demand for the remainder. In a typical screening operation coke pieces smaller than 3 inches are separated out of the coke being fed to the cupola, while the secondary screening operation separates particles under 3/4 of an inch from the fines.
The present invention is directed to employing the smaller fines in briquette form for use in the iron making process as a substitute for raw coke.
While briquettes of ferrosilicate or other additives have been employed in foundries, such briquettes are used in relatively small quantities and are conventionally hand fed into the cupola. Attempts in the past to provide coke in briquette form have been made, but have been found to be unsatisfactory. The most common problem encountered in previous coke briquetting attempts has been that the briquettes themselves are too brittle to withstand bulk handling and crumble or break up into fines, thus again contributing to the problem which they are attempting to solve. Where sufficient binder has been employed in prior briquettes to satisfy the brittleness or crumbling problems, the amount of binder employed is so high that it creates an unsatisfactorily high amount of slag within the cupola.
A briquette according to the present invention has been found to possess ample resistance to crumbling or fracturing during bulk handling operations and, in addition, contributes to the iron making process by functioning as a flux so that reduced quantities of limestone, a conventional fluxing agent, can be employed with the briquettes are used.